Abrasive device



June 15, 1965 A. BLOCK ABRASIVE DEVICE Filed April 27, 1962 United States Patent O 3,188,777 ABRASVE DEVICE Aleck Block, Los Angeles, Calif., assigner to Merit Products, Inc., Los Angeles, Calif., a corporation of California Filed Apr. 27, 1962, Ser. No. 199,639

9 Claims. (Cl. 51-337) This invention relates to a flap-type abrasive wheel wherein an annular array of flexible abrasive leaves is mounted on a rotary hub structure with individual leaves extending radially therefrom for abrasive action on a workpiece. The leaves are commonly made of cloth with hard sharp particles of abrasive material such as aluminum oxide or silicone carbide bonded to one face of the cloth.

The desired function of such a Wheel is to provide two kinds of abrasive action on a workpiece. One abrasive action is a slapping action of initial contact of each successive leaf against the workpiece and the other abrasive action is a following wiping action as the leaf moves beyond the point of initial contact. Each leaf working alone is too iexible for effective abrasion by its wiping action but the successive leaves are spaced close enough to each other to pack together at the wiping zone,y each wiping leaf being reinforced and backed by a number of follow- ,ing leaves.

- Unfortunately each successive leaf not only slaps against the workpiece but also slaps against the cloth back of the inew abrasive wheel.

For a relatively fast abrasive action on a workpiece, as

n many leaves as possible are commonly used in an annular array of leaves with no spacing between the anchored ends of the individual leaves to cause the maximum number of leaves to pack together for creating relatively high abrasive pressure against the workpiece. Unfortunately, however, using the maximum number of leaves in the array also results in relatively high pressure of leaf against leaf, to result'in fast Wear on the backs of the leaves.

One solution heretofore Iadvanced 'for this problem is to yinterpose lsmooth spacer leaves between the successive `abrasive leaves, the annular array consisting of abrasive leaves and alternate smooth paper leaves. lCounting the spacer leaves along with the abrasive leaves, this solution employs the maximum number of leaves to achieve relatively high wiping pressure against a workpiece and the solution does protect the cloth backs of the abrasive leaves against laceration. An economical disadvantage of the solution, however, is that the abrasive potential of the array of leaves, i.e. the total area of the abrasive leaves available for processing workpieces, is reduced by half.

The present invention eliminates the abrasive wear on the clothY backs of the abrasive leaves without incurring this economic disadvantage. This object is accomplished byV thesimple expedient of arranging the abrasive leaves foffthearray in successivev pairs with the abrasive faces `of the two leaves of each pair facing each other. Thus ytheannular array of abrasive leaves comprises two sets yof yalternate leaves facing in opposite rotary directions.

,y An unexpected advantage of this solution to the problern is thatabrasive wear among the leaves of the array is reduced in two ways. In the iirst place the abrasive actiongof each leaf is directed against the abrasive face of the next leaf and since the two opposed surfaces are Mice of equal hardness and abrasive resistance, relatively little wear is created. In the second place, the abrasive particles of the confronting abrasive faces of the pairs of leaves interlock to reduce slippage between the abrasive faces.

For those operations where relatively high abrasive pressure against a workpiece is desirable, the new arrangement has a further advantage in increasing the pressure. The abrasive pressure is increased because the interlocking of the abrasive particles of the confronting abrasive faces of each pair of leaves has the effect of increasing the resistance to iiexure of the pair.

Since all the leaves of the annular array of pairs of leaves are functional abrasive leaves, the maximum abrasive potential is afforded, i.e. the maximum total of abrasive leaf area is available for processing workpieces. It is a simple matter to reverse the direction of rotation of the hub structure to change from abrasive action by one of the sets of leaves facing in one rotary direction to abrasive action by the other set facing in the opposite rotary direction.

An important feature of one form of the invention is that the two sets of abrasive leaves are of different grades, one set having relatively fine abrasive particles and the other set having relatively coarse abrasive particles. After initially abrading a workpiece with the relatively coarse abrasive particles, it is merely necessary to reverse the direction of rotation of the abrasive wheel to switch to a finishing abrasive operation with liner abrasive particles. rfhus the invention provides a dual purpose abrasive wheel having the versatility of a set of two different abrasive wheels and the abrasive potential of the dual purpose wheel is equal to the combined abrasive potential of two separate abrasive wheels that incorporate alternate nonabrasive spacer leaves.

A further feature of the invention is the concept of spacing apart the anchored or root portions of the abrasive leaves at the circumference of the hub structure to modify ,the abrasive action of the wheel for operations where a softer `or more yielding abrasive action is desirable. When a workpiece is inserted into the outside circumference of a flap-type abrasive wheel, the leaves are deflected or inclined backwards with respect to the direction of r0- .tation by contact with the workpiece. There is a limit to which the leaves can be inclined backward, however, the limit being at what may be termed the solid diameter or radius at which no voids remain between the inclined closely packed leaves. In a conventional flap-type abrasive wheel, i.e. an abrasive wheel having the maximum number of leaves, for example a wheel in which the radial dimension of the hub structure relative to the axis of rotation is 2% inches and the abrasive leaves extend radiaily outward ve inches from the axis, the solid radius of the wheel is found to be approximately 41/2 inches, and the wheel may be said to have a yielding depth of 1/2 inch. lf a flat workpiece held substantially tangentially of the abrasive wheel is inserted 1A inch into the rotating annular array, only 1,41 inch remains of the yielding depth and, with the workpiece only 1A inch from the solid radius, the yielding resistance of the abrasive Wheel is relatively high to result in correspondingly relatively high abrasive pressure against the workpiece. It has also been found that providing the abrasive wheel with the maximum number of abrasive leaves results in an excessive number of leaves packing together in the region of contact with the workpiece, the consequent mutual reinforcement of the leaves tending to create relatively high abrasive pressure against the workpiece. It has been further found that excessive packing together of the leaves practically eliminates freedom for slapping action of the individual leaves against the workpiece.

Reducing the number of abrasive leaves to half by spacing the root portions of the leaves apart by the thickness of one leaf not only reduces the solid radius to increase the yielding depth of the abrasive wheel Vto approximately 11A inches, but also reduces the number of leaves thatv pack together in mutual reinforcement in the region yof contact with the workpiece. Consequently a workpiece lyl ing 1A inch inside the outer circumference of the annular array of leaves is subjected to a lighter and more yielding abrasive action. In addition, the individual leaves are .free for the desired slapping action against the workpiece.

4If the number of leaves is reduced to 1A of the maximum number of leaves by spacing the Vroot portions vof theV leaves apart bythe thickness lof two leaves, the result is further reduction in the severity of the abrasive action.

The `yielding depth of the abrasive wheel is increased to more thanll/z inches and only a relatively few leaves pack together to create abrasive pressure in the region of contact with the workpiece.-

The features and advantages Vof the invention may be understood by reference to the following detailed descrip'- tion and the accompanying drawing. l

In the drawing, which is to be regarded as merely illustrative:

FIG. 1 is a side elevation of a selected embodiment of Y the invention; Y

FIG. 2 is a diametrical section taken along the line 2-2 of FIG. 1;

FIG. 3 is a fragmentary Vportion of FIG. 1 greatly enlarged to show how the abrasive leaves are arranged in pairs with mutually opposed abrasive faces;

FIG. 4 is a diagrammatic side elevational view showing how the leaves tlex and crowd together in the region of contact with a flat surface of a workpiece;

FIG. 5 is a fragment of FIG. 4 greatly enlarged;

FIG. 6 is a fragmentary side elevational view showing how inner end portions of the leaves may be folded to serve as spacers to result in the root portions of the leaves being spaced apart by the thickness of one leaf;

their abrasive faces turned toward each other, each pair comprising an abrasive leaf 22a .and an abrasive leaf 22b. The abrasive leaf 22a of each pair has an abrasive face 33 and a smooth back or face 40 and the abrasive leaf 22b of each pair has an abrasive face .42 and a smooth back or face 44. While the abrasive faces 38 and 42 of the confronting abrasive leaves may be of the same grade, in this instance the abrasive faces 38 of the leaves 22a comprise abrasive particles of relatively line size and `the abrasive faces 42 of the leaves 22b comprise coarser abrasive particles. i

FIG. 4 shows how the abrasive leaves are iiexed by contact with a workpiece having a flat surface, the flatK sutrlface being indicated by the straightA line 45.y FIG. 5 is Aan enlarged detail of the same view. Itvmay be readily appreciated that the abrasive particles of the con-fronting Y abrasive faces 38 and 42 of the pairs of leaves 22a and FIG. 7 is a similar view showing spacers interposedbe- 'tween the successiveleaves to space the leaves apart by the thickness of two leaves; y

FIG. 8 is a similar view showing how spacers may be employed only between `the successive pairs of leaves, v

annular array or assembly, generally designated 20, of

individual abrasive leaves 22 is mounted on a hub structure, generallydesignated 24. As shown in FIG.` 2, the hub structure 24 includes a spindle 25 for rotary actuation by a suitable motor, the spindle having a screw thread 28. Two opposite side plates 30 are Slidingly mounted on the spindle 25 to clamp the assembly of abrasive leaves 22 from opposite sides, the two side plates being confined between a pair of nuts 32 and 33. As further shown in FIG. 2, the annular assembly 20 of abrasive leaves isf formed with two concentric circular grooves 35 on the Aopposite sides respectively of the assembly and the two side plates 30' are formed with inwardly turned'circular anges 36 which seat into the two grooves for leffective anchorage of the abrasiveleave's against centrifugal force.

The abrasive leaves 22are of a well-known construction-V comprising pieces of cloth'with yabrasive particles bonded on one face of the cloth, the opposite face ofthe cloth being smooth. In a conventional abrasive wheel of this character, the abrasive lfacesof the abrasive leaves all face in the samedirection of rotation.V vInthe present inopposite directions.

'nular array 20 comprises successive pairs ofjleaves with 22h tend to interlock to, resist slippage between the two abrasive faces. vSlippage does occur, however, to expose tip portions of the abrasive leaves 22a for abrasive action Von the workpiece but, nevertheless, the slippage is reduced in magnitude and is mater-iallyless than would occur between smooth surfaces; Thus'there is less slippage bet-ween the confronting abrasive facesl 38and 42 inside each pair .of leavesv22a yand 22h than occurs between the confronting smooth back faces V40 and 44 between the successive pairs of leaves. In effect the resistance to slippage betweenthe two confronting abrasive faces of a pair of leaves 22a and 22h causes the two leaves of the pair to reinforce each other against flexure by the workpiece. Thus the new arrangement of oppositely facing leaves has Ya stilfening effect to increase thev pressure of the abrasive leaves against the surface of the workpiece.

i It is further apparent that although all of the abrasive leaves 22a and'22b slip and rub on each other in a cyclic manner in t-he course of eachvrotation-of the abrasive wheel, nevertheless actual wear of leaf on leaf is: very Islight because all of thel mutually rubbing surfaces are of equal hardness. Since the confronting abrasive surfaces are of equal hardness, they do not create any significant wearon eachother even though they are' abrasive. Since the confronting smooth cloth back faces 40 and 44 are not only of equal hardnessy but also are non-abrasive, no significant wear occurs on the backs of the abrasive leaves. In fact after long usage, the backs of the abrasive leaves :show no indication of wear whereas in a conventional abrasive' wheel where all of the abrasive surfaces face in the same direction of rotation, substantial laceration of the cloth backs Vof the leaves may be observed after only 'a short period of service; i v

I t is apparent that the operation of the abrasive wheel may bey converted from abrasion with relatively coarse particles to abrasion with relatively line particles or viceversa, by merely reversing the direction of rotation of the wheel. Thus if the abrasive wheel is driven by a reversible motor it is merely necessary to reverse the motor to change from abrasionfwithone grade ofparticles to abrasion with a different grade of particles. If the motor is not reversible, the position of the abrasive wheel may be reversed on the spindle 25 to switch from Vone operation to the other whenever desired.

As heretofore stated, the maximum number of abrasive leaves is employed in a conventional flap-type abrasive wheel. VIn the first embodiment, of the invention shown in FIGS. 1-5the maximum `number of abrasive leaves 1s also employed, there being no'spacing between the anchored portions of the successive'leavesZZ, the leaves being packed Ysnlllglytogether inthe -region of the circumference1 of the huh structure 24. ,'As, heretofore stated, 1however, the yuse .of the maximum number of abrasive'leaves results V'in the annular ,array of leaves having a relativelyfshallow yielding Y'depth Vmeasured to the solid diameter of the array and such .an abrasive wheel exerts relatively heavy .abrasive *pressure on a.

workpiece. In addition' the abrasive pressure rises exponentially if the depth of penetration of the workpiece into the outer circumference of the annular array is increased. Thus the depth of penetration is critical with respect to control of the abrasive pressure on the workpiece.

Also, as heretofore stated, the yielding depth of the abrasive wheel may be increased, the abrasive pressure against the workpieces` decreased, and the depth of penetration made less critical by reducing the number of abrasive leaves in the annular array. FIG. 6, for example, shows how inner end portions 46 of the abrasive leaves may be folded to serve as spacers between the successive leaves at the anchored ends of the leaves in the region of the circumference of the hub structure of the abrasive wheel. Thus the successive oppositely facing abrasive leaves 52a and SZb of FIG. 6 are spaced apart by the thickness of a single leaf and the total number of leaves is reduced by half. It has been found that the construction indicated in FIG. 6 reduces the number of leaves that are crowded together in mutual support in the region of contact with the workpiece, this factor having the effect of reducing the abrasive pressure against the workpiece. It has also been found that the construction shown in FIG. 6 provides greater freedom for the desired slapping action by the individual leaves in their initial contacts with a workpiece.

FIG. 7 shows how the number of abrasive leaves may be reduced even further by employing spacers 54 between the successive leavesy of an array, the leaves comprising successive pairs of leaves 62a and 62h with confronting abrasive faces. In this instance the spacers 54 are of approximately twice the thickness of an abrasive leaf, the array having only one-third of the maximum leaves employed in a conventional abrasive wheel.

FIG. 8 illustrates another practice of the invention in which spacers 64 are employed only between the successive pairs of leaves, not between the leaves of each pair. An advantage of this arrangement is that it not only increases the yielding depth of the abrasive wheel but also has a selective effect in tending to increase the freedom for slippage between the confronting smooth back faces of the leaves.

FIG. 9 illustrates another practice of the invention in which spacers '74 are employed only between the two leaves of each pair, there being no spacing between the successive pairs. Thus the spacers 74 space apart the abrasive faces of each pair of leaves, there being no spacing between the exposed smooth back faces of the abrasive leaves. This construction may be used where it is desirable to reduce to some degree the interlocking action between the confronting abrasive faces. Thus if the resistance to slippage between the mutually opposed abrasive faces is found to be excessive, the spacers 74 may be used to give the opposed abrasive faces more freedom for slippage.

My description in specific detail of the selected embodiments of the invention will suggest various changes, substitutions and other departures from my invention within the spirit and scope of the appended claims.

I claim:

1. In an abrasive device, the combination of a rotary hub structure;

an annular array of leaves free at one and and anchored at the other end to the hub structure to act on a workpiece by a slapping action and a wiping action, each of said leaves having a non-abrasive face on one side and an abrasive face on the other side covered with abrasive particles, said leaves of the array being arranged in successive pairs with the abrasive faces of the leaves facing in a direction of rotation with the leaves of each pair confronting each other for abrasive action at the free end of the leaves -in both of the opposite directions of rotation of the hub strucyture and to resist relative sliding action bet-Ween the leaves of each pair.

2. A combination as set forth in claim 1 in which each of said pairs of leaves comprises a leaf with relatively ne abrasive particles and a leaf with relatively coarse abrasive particles, al1 of the leaves with relatively fine abrasive particles facing in one direction of rotation of the hub structure whereby the hub structure may be rotated in one direction to apply the relatively tine abrasive particles to a workpiece and may be rotated in the opposite direction toy apply the relatively coarse abrasive particles to a workpiece.

3. A combination as set forth in claim 2 wherein the anchored ends of the leaves are spaced by a distance of at least one thickness of the leaf to soften the abrasive action of the leaves against the workpiece.

4. A combination as set forth in claim 1 in which the anchored ends of said leaves are spaced apart by a distance on the order of one to two thicknesses of a leaf to lessen the solid diameter of the array and soften the abrasive action of the array against the workpiece.

5. In an abrasive device, the combination of:

a rotary hub structure;

an annular array of leaves free at one end and anchored at the other end to the hub structure to act on a workpiece by a slapping action and a wiping action, each of said leaves having a non-abrasive face on one side and an abrasive face on the other side covered with abrasive particles, said leaves of the array being arranged in successive pairs with the abrasive faces of the leaves of each pair confronting each other for abrasive action at the free ends of the leaves in both of the opposite directions of rotation of the hub structure and to resist relative sliding action between the leaves of each pair, the anchored ends of the leaves with confronting non-abrasive faces being contiguous, the anchored ends of the two leaves of each pair of leaves with confronting abrasive faces being spaced apart by at least approximately the thickness of one leaf.

6. A combination as set forth in claim 5 in which each of said pairs of leaves comprises a leaf with relatively ne abrasive particles and a leaf with relatively coarse abrasive particles, all of the leaves with relatively line abrasive particles facing in one direction of rotation of the hub structure whereby the hub structure may be rotated in one direction to apply the relatively fine abrasive particles to a workpiece and may be rotated in the opposite direction to apply the relatively coarse abrasive particles to a workpiece.

7. In an abrasive device, the combination of a rotary hub structure;

an annular array of leaves free at one end and anchored at the other end to the hub structure to act on a workpiece by a slapping action and a wipingy action, each of said leaves having a non-abrasive face on one side an an abrasive face on the other side covered with abrasive particles, said leaves of the array being arranged in successive pairs with the abrasive faces of the leaves of each pair confronting each other for abrasive action at the free ends of the leaves in both of the opposite directions of rotation of the hub structure and to resist relative sliding action between the leaves of each pair, the anchored lends of the confronting leaves of each pair being contiguous, the successive pairs of leaves at their anchored ends being spaced apart by at least approximately the thickness of one leaf.

8. A combination as set forth in claim 7 in which each of said pairs of leaves comprises a leaf with relatively fine abrasive particles and a leaf with relatively coarse abrasive particles, all of the leaves with relatively fine abrasive particles facing in one direction of rotation of the hub structure whereby the hub structure may be rotated in one direction to apply the relatively ne abrasive particles to a workpiece and may be rotated in the op- 7 8 posite direction to apply the relatively coarse abrasive -Y 2,508,073 5/5() 'Millerr "51-193 particles to a workpiece.; Y 2,678,523 Y Y5/547 Leggett V 51-193.5 9. Thel Combination'set forth in claim 7 wherein a "2,707,856 5/55 Kirkman 5'1-195 spacer is disposed-between' the leaves of each pair, 2,798,343 "7/57 Block l51-337 v Y 5 2,818,691 1/58 Leggett 51- 193.5 References Cited by the Examiner n3,078,624 2/63-- 'l Peterson 51--334 UNITED STATES PATENTS FOREIGN PATENTS Y 968,431 8/10 Stevens 15-230.14 Y 136,079 6/52 Sweden 1,011,323 12/11 Courtney a 15-23014 f l 2,109,905 3/38 Lippitt 51 ;193 .10 LESTER M. SWINGLE, Prlmktly'Exmmer.

2,455,680v 12/48 v,Kaplan 51e-193 FRANK BRONAUGH, JOHN c. CHRISTIE, 2,506,288 s/so Bahr 15-'23014 y y Y Y Examiners. 

1. IN AN ABRASIVE DEVICE, THE COMBINATION OF: A ROTARY HUB STRUCTURE; AN ANNULAR ARRAY OF LEAVES FREE AT ONE END AND ANCHORED AT THE OTHER END TO THE HUB STRUCTURE TO ACT ON A WORKPIECE BY A SLAPPING ACTION AND A WIPING ACTION, EACH OF SAID LEAVES HAVING A NON-ABRASIVE FACE ON ONE SIDE AND AN ABRASIVE FACE ON THE OTHER SIDE COVERED WITH ABRASIVE PARTICLES, SAID LEAVES OF THE ARRAY BEING ARRANGED IN SUCCESSIVE PAIRS WITH THE ABRASIVE FACES OF THE LEAVES FACING IN A DIRECTION OF ROTATION WITH THE LEAVES OF EACH PAIR CONFRONTING EACH OTHER FOR ABRASIVE ACTION AT THE FREE END OF THE LEAVES IN BOTH OF THE OPPOSITE DIRECTIONS OF ROTATION OF THE HUB STRUCTURE AND TO RESIST RELATIVE SLIDING ACTION BETWEEN THE LEAVES OF EACH PAIR. 